#include <bits/stdc++.h>
#define rep(i,n) for(int i = 0; i < (int)(n); i++)
#define rrep(ri,n) for(int ri = (int)(n-1); ri >= 0; ri--)
#define rep2(i,x,n) for(int i = (int)(x); i < (int)(n); i++)
#define rrep2(ri,x,n) for(int ri = (int)(n-1); ri >= (int)(x); ri--)
#define repit(itr,x) for(auto itr = x.begin(); itr != x.end(); itr++)
#define rrepit(ritr,x) for(auto ritr = x.rbegin(); ritr != x.rend(); ritr++)
#define ALL(x) x.begin(), x.end()
using ll = long long;
using namespace std;

int main(){
  int n;
  cin >> n;
  vector<int> a(n);
  rep(i, n) cin >> a.at(i);
  vector<int> b(n);
  rep(i, n) cin >> b.at(i);
  ll suma = 0, sumb = 0;
  ll ans = 0, diff = 0;
  rep(i, n){
    if(b.at(i)-a.at(i) > 0) ans += b.at(i)-a.at(i);
    else diff += a.at(i)-b.at(i);
    suma += a.at(i);
    sumb += b.at(i);
  }
  if(n == 2){
    if(suma != sumb){
      cout << -1 << endl;
      return 0;
    }
  }else{
    cerr << suma << " " << sumb << " " << ans << " " << diff << endl;
    if(suma < sumb || (suma - sumb) % (n-2) != 0){
      cout << -1 << endl;
      return 0;
    }
    ans = (suma-sumb)/(n-2);
    ll co = 0;
    rep(i, n){
      a.at(i) -= ans;
      if(b.at(i) < a.at(i) || (b.at(i) - a.at(i)) % 2 != 0){
        cout << -1 << endl;
        return 0;
      }
      co += (b.at(i)-a.at(i))/2;
    }
    if(co != ans){
      cout << -1 << endl;
      return 0;
    }
  }
  cout << ans << endl;
  return 0;
}